LDH blood test
Lactate dehydrogenase
In short
A typical adult LDH result is 122 to 222 U/L. A mild rise is common, and hard exercise or a damaged sample often explains it. Because LDH comes from many tissues, doctors use other tests to find the source. Always read your result against the range printed on your own report.
An enzyme found in almost every cell of the body.
LDH helps cells make energy, and almost every tissue has it. When cells are damaged anywhere, such as in muscles, the liver or red blood cells, LDH leaks into the blood. Because it comes from so many places, a high result doesn't show where it came from.
Is my LDH high or low?
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Typical range
| For | Range | Unit |
|---|---|---|
| Adults | 122–222 | U/L |
Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.
If your LDH is high
A mild rise is common, and hard exercise or a damaged sample often explains it. Because LDH comes from many tissues, doctors use other tests to find the source.
Common reasons
- Red blood cells broken in the tube during a difficult draw
- Hard exercise or a muscle injury
- Some medicines, including some pain relievers
- A recent infection, such as mono (mononucleosis) or pneumonia
- Less often: red cells breaking down too fast (hemolysis) or very low vitamin B12
- Less often: liver, lung, kidney or heart damage, or some cancers
If your LDH is low
A low LDH is uncommon and is rarely a concern.
Common reasons
- Normal variation between people
- Large doses of vitamin C or vitamin E
- Less often: a rare inherited change in the LDH enzyme
What can throw it off
A difficult blood draw or a shaken or delayed sample can break red cells and falsely raise LDH.
Questions to take to your appointment
- 1Could my blood sample have been damaged during the draw?
- 2Could recent exercise or a muscle strain explain this?
- 3Which other tests would show where the rise comes from?
Read together with
Doctors rarely read LDH alone. These usually sit next to it.
- HemoglobinThe protein in red blood cells that carries oxygen.
- Reticulocyte countYoung red blood cells, showing how fast new ones are made.
- Indirect bilirubinThe part of bilirubin the liver has not yet processed.
- ASTAn enzyme found in the liver, muscles and heart.
- CKAn enzyme that leaks from muscles after hard use or injury.
Quick answers
What is the LDH blood test?
LDH (Lactate dehydrogenase): An enzyme found in almost every cell of the body. LDH helps cells make energy, and almost every tissue has it. When cells are damaged anywhere, such as in muscles, the liver or red blood cells, LDH leaks into the blood. Because it comes from so many places, a high result doesn't show where it came from.
What is a normal LDH level?
For most adults, LDH is typically 122 to 222 U/L. Labs differ a little, so the range printed next to your result is the one to go by.
What does a high LDH mean?
A mild rise is common, and hard exercise or a damaged sample often explains it. Because LDH comes from many tissues, doctors use other tests to find the source. Common reasons include red blood cells broken in the tube during a difficult draw; hard exercise or a muscle injury; some medicines, including some pain relievers; and a recent infection, such as mono (mononucleosis) or pneumonia. A doctor reads it together with your other results and how you feel.
What does a low LDH mean?
A low LDH is uncommon and is rarely a concern. Common reasons include normal variation between people; large doses of vitamin C or vitamin E; and less often: a rare inherited change in the LDH enzyme.
What can affect my LDH result?
A difficult blood draw or a shaken or delayed sample can break red cells and falsely raise LDH.
What should I ask my doctor about my LDH?
Questions worth taking to the appointment: Could my blood sample have been damaged during the draw? Could recent exercise or a muscle strain explain this? Which other tests would show where the rise comes from?
What this page can’t do
It reads each number on its own.
Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.
It doesn't know you.
Your age, your medicines, how you feel and your last result all change what a number means.
It doesn't remember.
Close this page and your results are gone. That's on purpose: nothing was ever sent to us.
We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.
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